This invention relates to the design of gas turbine engines, and more particularly to the characterization of bird impacts, which are a particular problem when such engines are used in aircraft.
Bird impacts can be very damaging to gas turbine engines, and it is necessary to design engines so that they can be safely run on for a period of time after an impact or, at the very least, safely shut down without causing danger to the aircraft or passengers.
The basic techniques for carrying out bird ingestion tests on gas turbine engines are well known, and need not be discussed in detail here.
In such a test, a soft body is fired at a known position on the inlet of the engine. The soft body may be either a dead bird or an artificial soft body designed to replicate closely the impact behavior of a real bird. Such artificial soft bodies are well known. In the following description, the term “bird” can generally be taken to refer either to a real bird or to an artificial soft body used in a test in place of a real bird. After an impacting bird first hits the structure of the engine (whether static or rotating structure) it will fragment. Damage may be caused to the downstream parts of the engine by these fragments, and the size and trajectories of the fragments will determine the extent of this damage. Normally, the fragmentation can be assessed by viewing photographs or video of the first impact. The observed fragmentation can then be used to model the behavior of the different parts of the engine following an impact, and thereby to design the engine to minimize damage from bird strikes.